This invention relates generally to a single point fuel injection system and, more particularly, to the mechanical, electromechanical and electronic portions of a fuel management system for delivering a charge of fuel to a specified opening intake valve of the engine from a single point in a throttle body.
The majority of automobiles being built today have fuel systems which are either controlled by means of a carburetor or a multipoint fuel injection system. While the multipoint fuel injection system has been found to be an improvement over the carburetor, it too has problems which require solution. The system being described herein is calculated to combine the advantages of both systems and either solve or ameliorate the inherent problems of the two systems.
In the case of a carburetor, while it has an advantage of low cost and low operating fuel pressure, there are many undesirable characteristics inherent to the use of a carburetor. For example, the operation of a carburetor provides a continuous flow of fuel, the quantity of fuel being determined by the position of the throttle. It has been found that the fuel is not properly atomized and entrained in the air flow through the throat of the carburetor. Without proper atomization, the fuel distribution to the various cylinders is uneven thereby causing a rich or lean mixture from one cylinder to another. This situation increases the objectionable emissions from the particular cylinder which is too rich or too lean relative to stoichiometric. Also, relative to a fuel injection system, the carbureted system is inherently inaccurate in its fuel control whereby all of the cylinders may be operating at a point different from optimum.
Further, carbureted systems are typically operated in an open loop mode of operation. With this type of operation, the output of the engine exhaust system is not sensed to determine the quality of combustion which is occuring in the engine. Under these circumstances, the optimum air/fuel ratio is not achieved and higher emission levels are again experienced.
The shortcomings of a carbureted system have been somewhat eliminated by certain multipoint fuel injection systems on the market. With a multipoint fuel injection system, the fuel management is provided with a rather precise control of the fuel being fed to the engine which results in improved driveability without unwanted surges, lower emission levels, convenient changes of the calibration of the system, and the system may be operated in a closed loop mode of operation.
However, multipoint fuel injection systems do have certain undesirable characteristics which, if overcome, would increase the use of injected fuel management systems. For example, a typical multipoint fuel injection system involves a higher cost in the initial installation due to the sophisticated injectors being utilized and the relatively higher cost for the control electronics. Also, due to the requirement of a precise fuel pulse being fed to each cylinder, the fuel distribution between cylinders may vary due to the fact that the injectors are not perfectly matched, one to the other. As is the case with a carburetor, unless the fuel is highly atomized and rapidly carried into the appropriate cylinder immediately upon injection of fuel into the air stream, wall wetting is experienced. In the situation where the wetting of the walls with fuel is occurring, fuel is unevenly distributed to the cylinders and results in an uneven air/fuel ratio from cylinder to cylinder. Also, with wall wetting, the fuel charge being fed to the same cylinder from one cycle to the next may vary depending on the amount of fuel on the walls of the manifold. Upon injection of a fuel pulse which wets the walls of the manifold, the cylinder will receive a leaner air/fuel ratio charge than required. Subsequently, the fuel on the walls of the manifold will be entrained into the air stream to create a rich air/fuel mixture, which air/fuel mixture is not directly controlled by the duration of the fuel injection pulse. This can result in power surges which deteriorates the driveability of the automobile.
With a multipoint system, there are problems involved in the hot starting of the automobile and hot fuel handling due to the fact that the injectors are positioned very close to the high heat areas of the engine, as are the fuel lines feeding the injectors. This creates vaporization of the fuel resulting in a low quantity of fuel being injected per pulse to create a lean air/fuel ratio. Further, the multipoint fuel injection system requires a high pressure fuel system with the inherent sealing problems and the cost of a high pressure pump.
With a multipoint fuel injection system, it is seen that an injector is provided for each cylinder of the engine thereby requiring a wholly self-contained injector at each cylinder. Further, the system requires a pressure regulator which is separate from the injectors and a plurality of fuel atomizers, one for each injector being utilized in the system. It is obviously desirable to integrate all of the various parts associated with a multipoint fuel injection system into a single unit having a single housing. This reduces the cost of the system and also increases reliability.